Shell and tube flooded evaporator is an integral part of a refrigeration system. In a typical refrigeration system there is an evaporator that cools the process fluid at the expense of boiling the refrigerant that is at a lower saturation temperature and pressure, a compressor that compresses the boiled off refrigerant to an elevated pressure and temperature, a condenser that condenses the high pressure refrigerant to liquid phase at the expense of heating the cooling medium, and an expansion device that drops down the pressure of the condensed refrigerant back to the low side which then enters the evaporator to repeat the above cycle again. This cycle is called the reverse Rankine cycle.
Enhanced surface tubes such as shown in U.S. Pat. Nos. 3,521,708, 3,696,861, 3,821,018, 4,018,264, 4,060,125, 4,179,911, 4,182,412, 4,216,826, 5,697,430, 5,933,953 and 6,457,516 are being used on a regular basis in flooded refrigerant evaporators to reduce the overall size and/or refrigerant charge. In a large capacity unit these high efficiency tubes could create so much vapor that sometimes it may cause negative effects in the upper sections of the evaporator tube bundle. Hence, resulting in no benefit at a higher cost. Therefore, it is desirable to design and fabricate a tube bundle with various kinds of tubes along the height of the bundle that would result in a most optimized and economical evaporator.